Engines, for example vehicle engines, are known to include aspirators or ejectors for producing vacuum. Typically, the aspirators are used to generate a vacuum that is lower than engine manifold vacuum by inducing some of the engine air to travel through a Venturi. It is known that the high speed flow of air through a Venturi produces a pressure drop capable of pulling fluid from associated devices requiring a vacuum assist, including, for example, a fuel vapor purging system or a brake boost device. The aspirators may include a check valve between the Venturi and the device requiring vacuum assist to regulate the direction of flow through the aspirator.
It is known to provide a bypass valve in an aspirator for increased flow capacity through the aspirator during certain conditions. For example, it may be desirable to purge or evacuate the fluid from a device attached to the aspirator in a very short amount of time. Although the Venturi tube in the aspirator may generate a significant pressure drop and, therefore, vacuum, the small dimensions of the Venturi may restrict the volume of flow such that the device cannot be purged as quickly as desired. Therefore, a second flow path or bypass is provided in the aspirator to permit higher flow volume from high pressure to low pressure under certain conditions. For example, when the pressure in a device requiring vacuum assist is higher than the outlet pressure of the aspirator, i.e., typically manifold pressure, the bypass valve will open to permit flow through the bypass by virtue of the pressure gradient, regardless of the operation of the Venturi. This flow through the bypass is in addition to the flow through the Venturi which results in a quicker purge of the attached device requiring vacuum assist.
In known aspirators like the one in co-pending Published Application No. US2015/0096637, the port opening through the bypass valve is located in the top of the flow path through which fluid discharges from the Venturi outlet to the aspirator discharge outlet. This location of the port opening is restrictive and limits the size of the bypass port through which fluid flow is possible. In some applications, the flow area through a top bypass port may not be sufficient. Merely increasing the size of the top opening is not an acceptable solution. Therefore, a new aspirator design is needed with an improved bypass valve having greater flow capacity. According to the present invention, one or more bypass ports are provided in the lateral sides of the discharge path, rather than the top. Because of the cross-sectional shape of the discharge path, positioning one or more bypass ports on the lateral sides of the discharge path provides greater flow area for improved operation. In addition, relocation of the bypass port from the top to the lateral sides of the discharge path permits a refinement of the discharge path profile to reduce or eliminate abrupt changes in cross-section that produce separation of flow from the interior wall, an undesirable effect that results in turbulent flow and noise.